i) Field of the Invention
This invention relates to adhesive compositions and products, and to the manufacture of such compositions and products, more especially the invention is concerned with an adhesive composition which can be cured on command or at a desired point in time, and products based on the composition; in particular the invention is concerned with a composition curable by curing radiation, but in which the surface cure is inhibited by oxygen.
ii) Description of the Prior Art
Adhesive compositions are employed in a variety of environments in which a bond or seal is to be formed between two closely spaced surfaces, and in the manufacture of laminates of different materials. They may be applied in a flowable form, for example, as a liquid, and allowed to cure or set to a solid mass in situ; or they may be applied in a tape form in which the adhesive composition forms a coating or layer on a supporting substrate or film.
Such compositions are usually multi-component formulations in which two or more components are admixed at the time of use whereafter chemical reaction between the components to form a cured composition commences. If the cure proceeds rapidly the formulation must be employed without delay. If cure retardants are employed to delay or retard the cure, prolonged periods are required to complete the cure, and in some cases this means that the product must be stored in a controlled atmosphere over a period of days to allow the cure to complete.
Various mastic products, for example, sealants and preformed tapes and strips are known for mounting window glass. These mastic products are employed to bond sheets of window glass together adjacent their peripheral edges, in spaced apart relationship with an air space therebetween; they are also employed as bonding mediums and sealants between the window glass and the supporting frame structure which is typically of metal.
The problems associated with retarded cure of adhesives are experienced in the window industry with these mastic products wherein stacks comprising pairs of bonded together window glass must be stored for several days to allow the cure to complete.
These mastic products contain a solvent and are flowable, uncured polymer materials. The flowable nature presents handling problems and may also result in undesirable migration of the polymer material across the window glass surface, which is aesthetically unacceptable.
In addition to their adhesive character, these mastic products are required to display other characteristics having regard to the environment in which they are to be used. Thus mastic products employed as sealants in window structures should be weather resistant and impermeable to moisture and water.